Antenna system

Abstract

An antenna system includes a ground element, a switch element, a first antenna, and a second antenna. The switch element is selectively closed or opened according to a control signal. The first antenna has a first feeding terminal. The first feeding terminal of the first antenna is coupled to a first signal source. The second antenna has a second feeding terminal and a grounding terminal. The second feeding terminal of the second antenna is coupled through the switch element to a second signal source. The grounding terminal of the second antenna is coupled to the ground element.

What is claimed is: 
     
       1. An antenna system, comprising:
 a ground element; 
 a switch element, selectively closed or opened according to a control signal; 
 a first antenna, having a first feeding terminal, wherein the first feeding terminal of the first antenna is coupled to a first signal source; and 
 a second antenna, having a second feeding terminal and a grounding terminal, wherein the second feeding terminal of the second antenna is coupled through the switch element to a second signal source, and the grounding terminal of the second antenna is coupled to the ground element; 
 wherein the first antenna comprises a first radiation branch, a second radiation branch, and a third radiation branch, the first radiation branch is coupled to the first signal source and the ground element, and the third radiation branch is coupled through the second radiation branch to the first radiation branch. 
 
     
     
       2. The antenna system as claimed in  claim 1 , wherein the second antenna is a PIFA (Planar Inverted F Antenna). 
     
     
       3. The antenna system as claimed in  claim 1 , wherein when the switch element is closed, the second antenna is configured to increase diversity gain of the antenna system. 
     
     
       4. The antenna system as claimed in  claim 1 , wherein when the switch element is opened, the second antenna is configured as an extension portion of the ground element, so as to increase radiation efficiency of the first antenna. 
     
     
       5. The antenna system as claimed in  claim 1 , wherein when the switch element is closed, the first antenna is used as a main antenna and the second antenna is used as an auxiliary antenna, and both the first antenna and the second antenna cover a low-frequency band from about 700 MHz to about 800 MHz and a high-frequency band from about 1700 MHz to about 2150 MHz. 
     
     
       6. The antenna system as claimed in  claim 1 , further comprising:
 a dielectric substrate, having a first surface and a second surface opposite to the first surface, wherein the ground element, at least a portion of the first antenna, and the second antenna are disposed on the first surface of the dielectric substrate, and wherein the other portion of the first antenna is disposed on the second surface of the dielectric substrate. 
 
     
     
       7. The antenna system as claimed in  claim 6 , wherein the first radiation branch and the second radiation branch are disposed on the first surface of the dielectric substrate, and the third radiation branch is disposed on the second surface of the dielectric substrate. 
     
     
       8. The antenna system as claimed in  claim 7 , wherein a vertical projection of the third radiation branch at least partially overlaps the first radiation branch. 
     
     
       9. The antenna system as claimed in  claim 6 , wherein the first radiation branch has a first end and a second end, the first end of the first radiation branch is coupled to the first signal source and the ground element, and the second end of the first radiation branch is open. 
     
     
       10. The antenna system as claimed in  claim 9 , wherein the first antenna further comprises a first inductor coupled between the first end of the first radiation branch and the ground element. 
     
     
       11. The antenna system as claimed in  claim 6 , wherein the second radiation branch has a first end and a second end, the first end of the second radiation branch is coupled to the first radiation branch, and the second end of the second radiation branch extends from where the second radiation branch couples to the first radiation branch, and the second radiation branch at least partially surrounds the first radiation branch. 
     
     
       12. The antenna system as claimed in  claim 11 , wherein the first antenna further comprises a second inductor coupled between the first end of the second radiation branch and the first radiation branch. 
     
     
       13. The antenna system as claimed in  claim 6 , wherein the third radiation branch has a first end and a second end, the first end of the third radiation branch is coupled through a via element to the second end of the second radiation branch, and the second end of the third radiation branch is open. 
     
     
       14. The antenna system as claimed in  claim 13 , further comprising:
 a supporting plate, disposed between the third radiation branch of the first antenna and the second surface of the dielectric substrate, the third radiation branch is disposed on the supporting plate, and the via element is penetrated through the supporting plate and the dielectric substrate. 
 
     
     
       15. The antenna system as claimed in  claim 1 , wherein the second antenna comprises a fourth radiation branch and a fifth radiation branch, the fourth radiation branch is coupled to the switch element and the ground element, and the fifth radiation branch is coupled to the fourth radiation branch. 
     
     
       16. The antenna system as claimed in  claim 15 , wherein the fourth radiation branch has a first end and a second end, and the first end of the fourth radiation branch is coupled to the switch element and the ground element. 
     
     
       17. The antenna system as claimed in  claim 16 , wherein the second antenna further comprises a third inductor coupled between the first end of the fourth radiation branch and the ground element. 
     
     
       18. The antenna system as claimed in  claim 16 , wherein the fifth radiation branch has a first end and a second end, the first end of the fifth radiation branch is coupled to the second end of the fourth radiation branch, and the second end of the fifth radiation branch is open. 
     
     
       19. The antenna system as claimed in  claim 18 , wherein the second antenna further comprises a fourth inductor coupled between the second end of the fourth radiation branch and the first end of the fifth radiation branch.